1. Field of the Invention
The present invention relates to a film transport device for winding and rewinding a film and also to a film using apparatus or an optical apparatus having the film transport device.
2. Description of Related Art
Film cartridges of the kind having a photographic film contained therein in its entirety before use of the film, as disclosed in U.S. Pat. No. 4,832,275 and U.S. Pat. No. 4,834,306, have been put into practical use.
The film contained in the film cartridge of this kind must be driven to be wound up and rewound by a film transport device. The film transport device is required to perform the following three basic transport driving actions. A first transport driving action is a thrust driving action which is performed to send the film out from the cartridge, after the apparatus is loaded with the cartridge, by imparting a rotating force to a spool disposed within the cartridge. A second transport driving action is a film winding driving action which is performed to drive a film winding shaft disposed within the apparatus to cause the film sent out from the cartridge to be wound on the film winding shaft. A third transport driving action is a film rewinding driving action which is performed to rewind the film back to the inside of the cartridge by driving the spool disposed within the cartridge.
In addition to the above three basic transport driving actions, there are the following two design requirements. A first requirement is either to cancel the thrust driving action on the intra-cartridge spool immediately after the film is thrust-driven out of the cartridge and wound on the film winding shaft to be subjected to the film winding driving action, or to make a speed at which the film is fed by thrust driving onto the outermost circumferential part of a coil of film on the film winding shaft coincide with a film speed obtained at the outermost circumference of the film coil on the film winding shaft. This is necessary for preventing the film from being caused to sag and slacken or stretch too tight by a difference in speed between the thrust driving action and the film winding driving action.
A second requirement applies to a case where the film must be wound again after rewinding the film not completely while one round of film winding driving is still in process. For example, in cases where magnetic recording is possible on the film, it becomes sometimes necessary to correct a magnetic record or to confirm magnetic information recorded on the film by rewinding and winding the film. In such a case, a winding force must be transmitted to the film winding shaft while the film is in process of being wound, and must be not transmitted to the film winding shaft while the film is in process of being rewound. In other words, during the film rewinding driving action, a film speed at the outermost circumference of film coiled on the spool within the cartridge and a film speed at the outermost circumference of film coil on the film winding shaft must be arranged to always coincide with each other. This is necessary for preventing the film from being stretched or loosely wound on the film winding shaft or inside of the film cartridge with the film driven to be rewound at two different speeds.
Known film transport devices arranged to meet the above-stated requirement for the three film transport driving actions and the two design requirements include devices disclosed in Japanese Laid-Open Patent Application No. HEI 10-239743 and U.S. Pat. No. 5,568,214.
The film transport device disclosed in Japanese Laid-Open Patent Application No. HEI 10-239743 is arranged as follows. In thrust-driving a film from inside of a film cartridge, a motor power is reduced in speed by a reduction gear to obtain a film winding force. The film winding force is transmitted from the reduction gear to a winding shaft gear disposed at a film winding shaft to obtain a driving force. The driving force is outputted from the film winding shaft to drive the cartridge. During the film rewinding driving action, a power change-over means is operated at a front stage of input to the film winding shaft to cut off any input to the film winding shaft, and the film rewinding driving action is performed on the cartridge through a second gear connection part which excludes the winding shaft.
The film transport device disclosed in U.S. Pat. No. 5,568,214 is arranged as follows. To prevent any driving force from being transmitted to the film winding shaft during the film rewinding driving action, a clutch is interposed in between the film winding shaft and a winding shaft gear which is coaxial with the film winding shaft. The driving force of the winding shaft gear is allowed to be transmitted to the film winding shaft only at the time of the film winding driving action. Unlike in the case of Japanese Laid-Open Patent Application No. HEI 10-239743, this arrangement obviates the necessity of arranging a power change-over means at the film winding shaft gear to be used for changing power transmission from the film winding driving action over to the film rewinding driving action. In other words, in this case, the film winding shaft gear can be left in a state of appearing to be constantly in connection with a motor.
In accordance with one aspect of the invention, there is provided a film transport device, in which a clutch is disposed between a spool and a spool gear arranged to drive the spool, and the output of a motor is transmitted to a film cartridge through the spool gear, so that the spool gear can be used as an idler gear, and the film transport device can be compactly arranged.
The above and other aspects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in connection with the accompanying drawings.